Asymmetry inπ+Photoproduction from a Polarized Target at 5 and 16 GeV

We have measured the asymmetry of the cross section for $\gamma p\to {\pi }^{+}n$ from a polarized target at 5 and 16 GeV. The range of four-momentum transfer was $0.02<~-t<~1.0$ Ge${\mathrm{V}}^2$. The ${\pi }^{+}$ mesons were produced in a polarized butanol target and detected with the Stanford Linear Accelerator Center $20-\frac{\mathrm{GeV}}{c}$ spectrometer. A sizable asymmetry was found at both 5 and 16 GeV, a typical value being -0.6 near $-t=0.3\mathrm{}$ Ge${\mathrm{V}}^2$. A small amount of data on the asymmetry of other photoproduction processes was also obtained.